Ehhalt, D. H. .FZJ* ; Schmidt, U.FZJ* ; Lowe, D. C. (Corresponding author)FZJ*

1981
Kernforschungsanlage Jülich GmbH, Zentralbibliothek, Verlag Jülich

Report No.: Juel-1756

Abstract: A new measurement technique for determining the very low formaldehyde (HCHO) concentrations in clean air is described. The method is based on the standard derivatisation of formaldehyde with 2,4-dinitrophenylhydrazine. The derivative, formaldehyde 2,4-dinitrophenylhydrazone, is seperated using high performance liquid chromatography and detected at 254 nm with a conventional UV absorbance detector. Formaldehyde was sampled using a specially developed battery powered portable apparatus. This equipment proved to be easy and convenient to operate, even in remote clean air locations where the formaldehyde mixing ratio and its natural variations are likely to be of especial interest in air chemistry. The sampling and analysis technique have been used to measure tropospheric mixing ratios at various places in Europe and New Zealand as well as during a ship cruise in the North and South Atlantic. In addition vertical profiles of the formaldehyde mixing ratio were obtained during several aircraft flights up to 7 km above the Eifel district of the Federal Republic of Germany. The results of the measurements show that formaldehyde mixing ratios in clean air are very low. At ground level, values are about 0.2 ppbv and decrease with altitude, with values under 0.1 ppbv at 7 km being observed. In clean maritime air no significant difference in the formaldehyde mixing ratio between the hemispheres was observed. In the mid Atlantic, diurnal variations of the formaldehyde mixing ratio showing weak maxima during the early afternoon were occasionally observed. These variations were attributed to the diurnal behaviour of the photochemical production and destruction of formaldehyde during stable weather conditions. Measurements in polluted air at Jülich in the Federal Republic of Germany and in the continental boundary layer showed high variable mixing ratios which were undoubtedly due to industrial and vehicular sources of formaldehyde.

1. Troposphäre (ICG-2)